[unreadable] Positron Emission Tomography (PET) is an in vivo analog of autoradiography and has the potential to become a powerful new tool in imaging biological processes in small laboratory animals. With the ever increasing number of human disease models (including cancer) in the small laboratory animals such as mice and rats, high resolution PET imaging of small animals can contribute unique information. The critical advantage of PET is that it allows functional information to be obtained non-invasively, so each animal can be studied repeatedly. Thus, it is clear that PET imaging of small animals is highly desirable. Clinical PET scanners used for human imaging are bulky, expensive and do not have adequate spatial resolution for small animal studies. Hence, dedicated, low cost instruments are required for conducting small animal studies with higher spatial resolution than what is currently achieved with clinical PET scanners. The goal of the proposed Phase II project is to investigate a novel approach to produce a prototype small animal PET imager with very high spatial resolution and high sensitivity. Commercial Potential: Nuclear medicine including positron emission tomography and single photon emission computed tomography, radiology, non-destructive testing, materials research, X-ray diffraction, nuclear and high energy physics research, astronomy, and geological exploration. [unreadable] [unreadable]